1. Field of Invention
The present invention relates to a canister unit, and more particularly, to a heater-integrated canister unit of which absorbing/detaching efficiency is improved by increasing the temperature of the charcoal in the canister.
2. Description of Related Art
In general, canister systems collect/store hydrocarbon (HC) in the evaporation gas produced by evaporation of fuel when a vehicle stops, travels, and fills a fuel tank, and send the collected/stored hydrocarbon (HC) to the combustion chamber, using engine intake pressure when the engine is turned on.
The canister systems include a canister filled with charcoal, an evaporation gas intake channel connected from a fuel tank to the canister, an evaporation gas exhaust channel connected from the canister to the combustion chamber of an engine, and an atmospheric pressure channel connecting the canister with the atmosphere.
Valves that are controlled to open/close by an electronic control unit (ECU) are disposed in the channels.
By using the canister systems, it is possible to collect/store hydrocarbon (HC) by sending the evaporation gas (air+hydrocarbon evaporation gas) in the fuel tank to the canister when a vehicle is filling the fuel tank or stopped, whereas it is possible to burn the hydrocarbon (HC) collected in the canister by sending the hydrocarbon to the combustion chamber using the intake pressure of the engine when the vehicle travels.
That is, the evaporation gas intake channel connecting the fuel tank with the canister and the atmospheric pressure channel connecting the canister with the atmosphere are opened when the vehicle is filling the fuel tank or stopped, whereas the evaporation gas exhaust channel connecting the canister with the combustion chamber of the engine and the atmospheric pressure channel connecting the canister with the atmosphere are opened when the vehicle travels.
In general, the performance of the canister system depends on the canister and the performance of the canister depends on the performance of the charcoal particles that adsorb and detach the hydrocarbon (HC).
PZEV (Partial Zero Emission Vehicle), which is an environmental rule in North America, reinforces a request of reducing emission, such as hydrocarbon (HC) contained in the evaporation gas from vehicles, and it is required to increase the performance and efficiency of canisters and the purge performance of an evaporation gas between an engine and a canister in order to satisfy the rule.
In particular, hybrid vehicles and ISG (Idle Stop and Go) vehicles in which the purge rate of a canister without purging in idling necessarily require a canister with increased capacity, which is based on that the reduction of purge rate of the canister increases the hydrocarbon (HC) remaining in the canister and DBL (Diurnal Breathing Loss), which is a regulated test, is decreased under a condition that is directly influenced by the DBL.
FIG. 10 shows a canister with increased capacity and performance installed in a fuel tank to satisfy PZEV, which is a reinforced environmental rule in North America.
As shown in the figure, a canister system includes a main canister 100 installed at a fuel tank 300 and a sub-canister 200 connected to main canister 100, such that the capacity and performance of the canister increases as much as sub-canister 200 provides, thereby satisfying PZEV.
However, the type of main canister 100 equipped with separate sub-canister 200 necessarily increases the cost and weight.
Further, the space for installing sub-canister 200 connected to main canister 100 changes the shape of fuel tank 300, such that it is difficult to ensure capacity of fuel tank 300, and the length increased by sub-canister 200 increases ventilation resistance of a fuel vapor system, such that resistance of air exhaust channel in fuel tank 300 increases.
In particular, the increase in resistance of the air exhaust channel in fuel tank 300 due to sub-canister 200 may make it difficult to fill a vehicle with fuel, or if excessive, may make it impossible to fill a vehicle with fuel.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.